The present invention relates to slide projectors and, in particular, to slide projectors having a rotary tray for retaining the slides during the projection operation.
Following the invention of the positive transparency, there have been a multitude of various systems proposed to view the image on the positive transparency. Positive transparencies are known more popularly as slides. In fact, at present, slides are among the most popular forms of amateur photography. Along with this popularity, there are numerous systems commercially available to project the image of the positive transparency onto a screen, or the like, for viewing. One of the most popular types of slide projectors is the type having a rotary slide tray or magazine. As the tray rotates, the slides are removed one at a time from the tray and placed in front of a light source. Light is projected through the slide, and an objective lens system forms the image on the screen. Typical of this type of slide projector is the Kodak Carousel model. In this instance, the rotary slide tray is arranged horizontally on the top of the projector housing and, as the Carousel slide tray is caused to rotate, a slide is permitted to drop through a slot in the bottom of the magazine down between the lamp and the lens system, where it is then projected onto the screen. When the desired projection time has ended, a mechanical linkage then raises the slide back to the slot whence it came, and the magazine then is advanced to the next slide. The operation then begins anew and the slide falls under the force of gravity into the projection system.
Another type of slide projector employs a rotary magazine arranged in a vertical position in relation to the projector housing, and uses a mechanical linkage to drive the slide out of the magazine slot into the projection system. At the end of the desired projection time, the mechanical linkage then drives the slide back into the magazine, the magazine is advanced to the next slide, and the operation is repeated.
There are additional types of slide projectors not employing rotary slide trays, which merely stack the slides, one upon each other, and then advance them in a linear manner. There are also rectangular slide trays for retaining the slides, which are linearly advanced and operate in the manner of the Carousel or other vertical rotary slide tray.
While certain of the presently available slide projectors employ the force of gravity to perform a portion of the slide transfer operation, none of these slide projectors can transfer a slide from the magazine to the projection lens and back to the magazine using only the forces of gravity. Moreover, in any mechanical system requiring an electrically-driven linkage to move elements, which are as small as a photographic slide and which have loose mechanical manufacturing tolerances, binding of the linkage and/or the slide is almost certain to occur. In fact, that is the principle problem in many slide projectors, i.e., that the slides tend to hang up in the magazine or in the changing mechanism, and jamming is a frequent occurrence.